Method and apparatus for carrying telephony network traffic over an ATM network

ABSTRACT

A method that sends ATM source identification and an ATM-TDM correlation tag from an ATM source gateway to a telephony signaling control network; and then receives at an ATM destination gateway the ATM source identification and the ATM-TDM correlation tag as sent from the telephony signaling control network; and then sends the ATM-TDM correlation tag from the ATM destination gateway to the ATM source gateway to establish a connection between the ATM destination gateway and the ATM source gateway.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from and is a divisionalapplication of U.S. patent application Ser. No. 09/752,075 filed on Dec.29, 2000, now U.S. Pat. No. 7,085,279, issued on Aug. 1, 2006.

FIELD OF THE INVENTION

The field of invention relates to networking, generally; and morespecifically, to carrying telephony traffic over an ATM network.

BACKGROUND

FIG. 1 shows an example of a traditional approach for carrying telephonytraffic. Telephony traffic is traditionally carried over a telephonynetwork 103. As is known in the art, a telephony network 103 employs: 1)circuit switching to set up a connection; and 2) time divisionmultiplexing (TDM) to transport information over the connection. Someexamples of a telephony network include a Public Switched TelephoneNetwork (PSTN) or an Integrated Services Data Network (ISDN).

Telephony traffic is traffic traditionally carried by a telephonynetwork such as voice traffic and facsimile (FAX) traffic. In theexample of FIG. 1, telephony traffic is carried by the telephony network103 from a source device 101 (e.g., a telephone mouthpiece ortransmitting FAX modulator) to a destination device 102 (e.g., atelephone earpiece or receiving FAX demodulator).

Note that, as an example, both the source device 101 and the destinationdevice 102 are coupled to a corresponding local exchange or end office180, 181 (LE/EO). A local exchange typically handles traffic from asmaller geographic region while a central exchange typically handlestraffic from a larger geographic region. Because either may apply to theexemplary depiction of FIG. 1, the notation LE/EO 180, 181 has beenused.

The source device 101 is coupled to LE/EO 180 (which may also bereferred to as the source LE/EO 180) and the destination device 102 iscoupled to LE/EO 181 (which may also be referred to as the destinationLE/EO 181). An LE/EO, such as source LE/EO 180, provides for theefficient collection of information from different source devices. Thatis, traffic entering the telephony network 103 (e.g., from a pluralityof different telephone mouthpieces and/or transmitting FAX modulators)may be combined at a LE/EO 180 and transported further upstream (i.e.,deeper into the telephony network 103) over a single trunk line 113(e.g., a T1 line).

Similarly, a LE/EO such as destination LE/EO 181 also provides efficientdistribution of information to different destination devices. That is,traffic leaving the telephony network 103 (e.g., toward a plurality ofdifferent telephone earpieces and/or receiving FAX demodulators) may becollectively received at a LE/EO from a single trunk line 118 (that iscoupled to deeper regions of the telephony network 103) and thendistributed from the LE/EO to the appropriate destination devices.

For any connection carried by the telephony network 103, theconnection's establishment (e.g., call setup and teardown procedures)and routing path are controlled by a telephony signaling control network104. An example of a telephony signaling control network 104 is aSignaling System 7 (SS7) network. SS7 networks, which include local andnational variants, are implemented world-wide.

As an example, when an individual at the source device 101 attempts tocall an individual at the destination device 102, the informationindicative of the source and destination devices (e.g., an InitialAddress Message (IAM) message) is typically forwarded from the sourceLE/EO 180 to a signaling transfer point (STP) 105 within the telephonysignaling control network 104. The STP 105 (which may also be referredto as the “source” STP 105) helps arrange notification of the call toSTP 106 (which may also be referred to as the “destination” STP 106)responsible for the destination LE/OE 181.

Upon such notification, the destination STP 106 will forward the IAMmessage to the destination LE/EO 181. The destination LE/OE will thennotify the destination device 102 of the call (e.g., via a “RING”signal). The destination LE/EO 181 is also informed, from the telephonysignaling control network 104, which TDM time slot on trunk line 118that the information from the call is to be sent along. Generally, whenmultiple switches (i.e., more than two) are used to carry a call, aswitch communicates the TDM time slot and trunk line (through thetelephony signaling control network 104) to the next switch used tocarry the call.

A problem with telephony networks is their inherent emphasis on thetransportation of telephony traffic. With the growth of the Internet,service demand for the transportation of data traffic (e.g., trafficbetween computing devices such as e-mails, HTML files, etc. exchangedbetween computers) has sharply risen. Unfortunately, the TDM approachemployed by a telephony network is a networking architecture that isparticularly tailored for the carrying of voice conversations. As aresult, a telephony network does not efficiently handle thetransportation of both voice and data traffic.

SUMMARY OF INVENTION

A method is described that sends ATM source identification and anATM-TDM correlation tag from an ATM source gateway to a telephonysignaling control network. At an ATM destination gateway, the ATM sourceidentification and the ATM-TDM correlation tag are received after beingsent from the telephony signaling control network. The ATM-TDMcorrelation tag is then sent from the ATM destination gateway to the ATMsource gateway to establish a connection between the ATM destinationgateway and the ATM source gateway.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and notlimitation, in the Figures of the accompanying drawings in which:

FIG. 1 shows a traditional telephony network and telephony signalingcontrol network;

FIG. 2 shows a call agent based telephony signaling control network thatuses traditional SS7 signaling and an ATM network; and

FIG. 3 shows a method for establishing a connection that transportstraffic from a telephony network over an ATM network.

DETAILED DESCRIPTION

A method is described that sends ATM source identification and anATM-TDM correlation tag from an ATM source gateway to a telephonysignaling control network. At an ATM destination gateway, the ATM sourceidentification and the ATM-TDM correlation tag are received after beingsent from the telephony signaling control network. The ATM-TDMcorrelation tag is then sent from the ATM destination gateway to the ATMsource gateway to establish a connection between the ATM destinationgateway and the ATM source gateway.

FIG. 2 shows a solution to the problem described in the background. Inthe approach of FIG. 2, an ATM network 207 is used as a “backbone” tocarry (e.g., over long distances) telephony traffic between twotelephony networks 203 a, 203 b. Because ATM employs cell switchingtechnology, ATM efficiently transports both voice traffic and datatraffic. As such, a service provider may be inclined to deploy ATMtechnology.

However, uses of a traditional telephony network may still be desirable.For example, to extend the original investment made in their own TDMequipment, customers of a service provider may decide to communicate tothe service provider through a traditional telephony network 203 a, 203b. In other cases, traditional telephony networks may be suitablebecause the transportation of data traffic to a particular region orcustomer is insignificant. Note that, in any of these cases, traditionaltelephony networks 203 a, 203 b may correspond to networks operated bythe service provider or a customer of the service provider or acombination of both.

In an embodiment, the ATM network 207 may approximately correspond to awide area network (WAN) that carries traffic over longer distances whiletelephony networks 203 a,b may approximately correspond to localnetworks that carry traffic over shorter distances (e.g., such as localexchange (LE) network or customer premise network). The networkarchitecture 200 of FIG. 2 indicates that traffic between a first andsecond telephony network 203 a, 203 b is carried by an ATM network 207.

That is, for example, if a call is made from a source device 201 to adestination device 202 (where the source device 201 is communicativelycoupled to a first telephony network 203 a and the destination device202 is communicatively coupled to a second telephony network 203 b), thecall is routed from the first telephony network 203 a through the ATMnetwork 207 and then from the ATM network 207 to the second telephonynetwork 203 b. In this manner, the transportation of the call istransparently carried as ATM traffic even though the source anddestination devices 201, 202 employ traditional telephony networktransportation techniques.

In a basic case, telephony network 203 a may correspond to a sourceLE/EO (such as source LE/EO 180 of FIG. 1) and telephony network 203 bmay correspond to a destination LE/EO (such as destination LE/EO 181 ofFIG. 1). In this case, trunk lines 213, 218 may respectively correspondto trunk lines 113, 118 (e.g., T1 lines) in the sense that they carrythe call from the source and destination LE/EOs 180, 181 to deeperregions of the network. It is important to note, however, that telephonynetworks 203 a, 203 b may be comprised of any equipment used toimplement a telephony network. As such, trunk lines 113, 118 are notnecessarily tied to an LE or OE.

The approach associated with FIG. 2 integrates the connectionestablishment capabilities of both the ATM network 207 and the telephonysignaling control network 204 so that an end-to-end connection from thesource device 201 to the destination device 202 may be realized. Inorder to realize such a connection, as described in more detail below,information is exchanged between the ATM network 207 and the telephonysignaling control network 204.

Recall from the discussion in the background concerning FIG. 1 that if asource device 101 attempts to call a destination device 102, informationindicative of the source and destination devices is typically forwardedto source STP 105. Referring to FIG. 2, a similar procedure may beapplied.

That is, communication interface 214 may correspond to communicationinterface 114. As such, when the source device 201 initiates a call tothe destination device 202, information indicative of the source anddestination devices (e.g., an IAM message, an ISDN setup message, anMGCP notification message) is forwarded over communication interface 214from the first telephony network 203 a to a telephony signaling controlnetwork 204.

Note that the communication interface 214 may be one of many differentmeans used for communicating telephony signaling information between atelephony network 203 a and a telephony signaling control network 204.Such means may include (but are not limited to including): SS7Integrated Services digital network User Part (ISUP) signaling, theMedia Gateway Control Protocol (MGCP), the ITU h.248 protocol, MEGACO,and an SCTP or RUDP based backhaul of ISDN signaling, etc.

After the telephony signaling control network 204 receives informationthat is indicative of the source 201 and destination 202 devices for theparticular call, the telephony signaling control network 204 helpsestablish the call path through the telephony network 203 a that iscoupled to the source device 201 by reserving appropriate resources andproviding appropriate signaling. The telephony signaling control network204 also decides that the call will be directed over a particular trunkline 213 that couples the telephony network 203 a to the ATM network207.

This decision may be based on trunk availability between telephonynetwork 203 and ATM network 207 by routing algorithms that are executedin the telephony signaling control network. Each trunk line 213, 218 mayalso be implemented as a “trunk group” or a “multiplexed line” and, assuch, may also be referred to as a “trunk group/multiplexed line”.

When the telephony signaling control network 204 receives the source anddestination information from the telephony network 203 a, notificationof the call (i.e., call notice) is sent from the telephony signalingcontrol network 204 to a source gateway 208 within the ATM network 207.The call notification may include a description of the particular TDMtime slot on trunk line 213 that will be used for the call. In caseswhere more than one trunk line 213 could apply, the call notice may alsodescribe which particular trunk line will be used for the call.

An ATM source gateway 208 provides access to the ATM network 207 (viatrunk line 213) for the telephony network 203 a that is coupled to thesource device 201. The interface 215 between the telephony signalingcontrol network 204 and the ATM source gateway 208 may take variousforms such as a gateway control protocol, a signaling backhaul protocolor a combination of the two. Examples of a gateway control protocolinclude (but are not necessarily limited to) MGCP, MEGACO and the ITUh.248 protocol. Examples of a signaling backhaul protocol include (butare not necessarily limited to) Stream Control Transmission Protocol(SCTP) and Reliable User Datagram Protocol (RUDP).

After the ATM source gateway 208 receives the call notice, it respondsto the telephony signaling control network (e.g., in the form of anacknowledgement) with: 1) an ATM source id (e.g., information thatreflects the position of the ATM source gateway 208 within the ATMnetwork 207 such as the ATM address of the ATM source gateway 208); and2) an ATM-TDM correlation tag (i.e., information that associates the ATMconnection that will be used to transport the call with TDM parameters(e.g., trunk line and TDM time slot) that will be used to transport thecall). Note that the ATM-TDM correlation tag may be a randomly generatednumber.

After the ATM source id and ATM-TDM correlation tag are received by thetelephony signaling control network 207 (e.g., by call agent 205), bothare sent from the telephony signaling control network 204 to an ATMdestination gateway 209. The telephony signaling control network 204also helps establish the remainder of the call path by reservingappropriate resources and providing appropriate signaling withintelephony network 203 b that is coupled to the destination device 202.Thus, information that is indicative as to which particular TDM timeslot on trunk line 218 that is being reserved for the call is also sentalong with the ATM source id and the ATM-TDM correlation tag from thetelephony signaling control network 204 to the ATM destination gateway209. An ATM destination gateway provides access to ATM network 207 fortelephony network 203 b.

A call agent, such as call agent 205 and call agent 206, are devicescapable of communicating with multiple protocols that may be used tocommunicate with a telephony signaling control network 204. For example,typically, a call agent not only communicates according to traditionalSS7 based signaling but also other communication protocols that may beused to interface with a telephony signaling control network (e.g.,MGCP, ITUh.248, MEGACO etc.). Thus, for example, if interface 215corresponds to an MGCP interface and if interface 214 corresponds to anSS7 based interface, a call agent may be used to understand thesignaling associated with both interfaces.

An ATM destination gateway 209 provides access to the ATM network 207(via trunk line 218) for the telephony network 203 b that is coupled tothe destination device 202. In an embodiment, as seen in FIG. 2, the ATMsource id and ATM-TDM correlation tag are forwarded from a source callagent 205 to a destination call agent 206 within the telephony signalingcontrol network 204. In a further embodiment, the ATM source id andATM-TDM correlation tag are sent through the telephony signaling controlnetwork 204 within an IAM message.

The destination call agent 206 then forwards the ATM-TDM correlation tagand ATM source id to an ATM destination gateway 209 over communicationinterface 216. The destination call agent 206 also helps establish, overcommunication interface 217, the call in the telephony network 203 bthat is coupled to the destination device 202. As such, the destinationcall agent 206 also informs the ATM destination gateway 209 as to whichTDM time slot on trunk line 218 is being reserved for the call. If morethan one trunk line exists the telephony signaling control network 204may also inform the ATM destination gateway 209 as to the proper trunkline to be used for the call.

Again, communication interface 216 may take various forms such as agateway control protocol, a signaling backhaul protocol or a combinationof the two. Examples of a gateway control protocol include (but are notnecessarily limited to) MGCP, MEGACO and the ITU h.248 protocol.Examples of a signaling backhaul protocol include (but are notnecessarily limited to) Stream Control Transmission Protocol (SCTP) andReliable User Datagram Protocol (RUDP).

Also, communications interface 217 may be one of many different meansused for communicating telephony signaling information between atelephony network 203 b and a telephony signaling control network 204.Such means may include (but are not limited to including): SS7Integrated Services digital network User Part (ISUP) signaling, theMedia Gateway Control Protocol (MGCP), MEGACO, the ITU h.248 protocol,an SCTP or RUDP based backhaul of ISDN signaling, etc.

Upon receipt of the ATM-TDM correlation tag and ATM source id, the ATMdestination gateway 209 initiates a switched virtual circuit (SVC)connection establishment sequence in which the ATM-TDM correlation tagis sent along with traditional switched virtual circuit (SVC) connectionsignaling from the ATM destination gateway 209 to the ATM source gateway208.

An SVC connection may be established by sending a SETUP message from aconnection destination within an ATM network (e.g., ATM destinationgateway 209) to a connection source within an ATM network (e.g., ATMsource gateway 208). The SETUP message typically propagates through theATM network 207 by hopping at each node that will be used to carry theconnection.

For example, referring to FIG. 2, if the connection is to be carriedover nodes 212, 211, and 210, (which may be determined as a result ofthe execution of a routing algorithm) the SETUP message traverses eachof these nodes. As a result of the SETUP message being sent, VPI/VCIinformation associated with the connection is updated into the mappingtables of each node used to support the connection.

In an embodiment, each SETUP message includes the aforementioned ATM-TDMcorrelation tag that was sent to the ATM destination gateway 209 by thetelephony signaling control network 204. SETUP messages without anATM-TDM correlation tag are known in the art. A SETUP message ispartitioned into various fields (which are referred to as InformationElements (IEs), similar to the manner in which a packet header isorganized. In one embodiment, the ATM-TDM correlation tag is placedwithin the Called Party Sub-Address IE of a SETUP message (e.g.,anywhere in the later 19 octets of this field). In another embodimentthe ATM-TDM correlation tag is placed within the Generic IdentifierTransport (GIT) IE. In another embodiment the ATM-TDM correlation tag isplaced within the Generic Application Transport (GAT) IE. In anotherembodiment, the ATM-TDM correlation tag is placed within the User toUser IE. In another embodiment, the ATM-TDM correlation tag is placedwithin the Network Call Correlation Identifier (NCCI) IE. In anotherembodiment, the ATM-TDM correlation tag is placed within the CallingParty Sub Address IE. In another embodiment, the ATM-TDM correlation tagis placed within the Served User Generated Reference IE (SUGR).Alternate embodiments may place the ATM-TDM correlation tag in otherregions of the SETUP message not listed above where such placement isconsistent with applicable industry standards.

Eventually, a SETUP message will reach the ATM source gateway 208. TheSETUP message received by the ATM source gateway 208 will include theATM-TDM correlation tag. Thus, in a sense, after the ATM-TDM correlationtag was created by the ATM source gateway 208 it was “looped” throughthe telephony signaling network 204 and the ATM network 207. Recall thatthe telephony signaling control network 204 (as part of the call noticepreviously provided through communication interface 215) has alreadynotified the ATM source gateway 208 as to which TDM time slot on trunkline 213 that the call will be carried over.

The ATM-TDM correlation tag is used by the ATM source gateway 208 tocorrelate the SETUP message with the particular TDM time slot on trunkline 213 that the call will be carried over. That is, recalling that theATM source gateway 208 originally generated the ATM-TDM correlation tagin light of notification of the call, upon receipt of the ATM-TDMcorrelation tag within the SETUP message the ATM source gateway 208 canupdate its mapping tables (or similar information) so that the payloadof cells sent from/to node 212 (having the appropriate VPI/VCIinformation for the connection) are transported to/from the trunk 213and TDM time slot that was specified by the telephony signaling controlnetwork 204.

Associated with this update, consistent with ATM SVC call establishmentsequencing, ATM source gateway 208 sends a CONNECT message to the ATMdestination gateway 209 through the nodes used to transport the call(e.g., nodes 212, 211, 210 as seen in FIG. 2). After the CONNECT messagehas been received by the ATM destination gateway 209, an end to endconnection between the source device 201 and the destination device 202has been established.

FIG. 3 shows a methodology that reviews, at a high level, the “looping”of the ATM-TDM correlation tag described above. Consistent with thedescription above, an ATM connection and ATM source id are sent 301 froman ATM source gateway to a telephony signaling control network. Then,the ATM-TDM correlation tag and ATM source id are sent 302 from thetelephony signaling control network to an ATM destination gateway. Then,the ATM-TDM correlation tag is sent 303 within the ATM network, via aSETUP message, from the ATM destination gateway to the ATM sourcegateway.

It is important to point out that the techniques described above may beemployed by any ATM network. Thus, these techniques may be employed notonly by a purely cell switched ATM network but also by an ATM AdaptationLayer Type 2 (AAL2) packet network. In this case, an Establish Request(ERQ) message is used instead of a SETUP message and an EstablishConfirm (ECF) message is used instead of a CONNECT message. Furthermore,rather than using VCI information, VCI/CID information is employed. ATMnetworks that comprise a combination of AAL2 packet and purely cellswitched architectures may also use these techniques if appropriatetranslation of the SETUP/ERQ and CONNECT/ERF messages are provided aswell as any needed bearer network conversions (e.g., from multiplexed tonon-multiplexed cells).

It is also important to point out that the methodologies may beimplemented at least partially with software. Thus it is to beunderstood that embodiments of this invention may be used as or tosupport software programs executed upon some form of processing core(such as a the CPU of a computer or an embedded microprocessor) orotherwise implemented or realized upon or within a machine readablemedium. A machine readable medium includes any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer). For example, a machine readable medium includes read onlymemory (ROM); random access memory (RAM); magnetic disk storage media;optical storage media; flash memory devices; electrical, optical,acoustical or other form of propagated signals (e.g., carrier waves,infrared signals, digital signals, etc.); etc.

1. A method, comprising: receiving a call notice from a telephonysignaling control network, the call notice including TDM parameters, theTDM parameters including a TDM time slot over which a call will becarried and a trunk line that couples an ATM source gateway to atelephony network, the TDM time slot being associated with the trunkline that couples the ATM source gateway to the telephony network;sending an acknowledgement to the telephony signaling control network,the acknowledgment is an ATM-TDM correlation tag having information thatassociates an ATM connection with the TDM parameters, the ATM connectionbeing used to transport the call from the ATM source gateway to an ATMdestination gateway; sending the ATM-TDM correlation tag to the ATMdestination gateway; and receiving said ATM-TDM correlation tag fromsaid ATM destination gateway as a SETUP message.
 2. The method of claim1 wherein said ATM-TDM correlation tag is within a Called Party SubAddress Information Element (IE) of said SETUP message.
 3. The method ofclaim 1 wherein said ATM-TDM correlation tag is within a GenericIdentifier Transport (GIT) IE of said SETUP message.
 4. The method ofclaim 1 wherein said ATM-TDM correlation tag is within a GenericApplication Transport (GAT) IE of said SETUP message.
 5. The method ofclaim 1 wherein said ATM-TDM correlation tag is within a User to User IEof said SETUP message.
 6. The method of claim 1 wherein said ATM-TDMcorrelation tag is within a Network Call Correlation Identifier (NCCI)IE of said SETUP message.
 7. The method of claim 1 wherein said ATM-TDMcorrelation tag is within a Calling Party Sub Address IE of said SETUPmessage.
 8. The method of claim 1 wherein said ATM-TDM correlation tagis within a Served User Generated Reference (SUGR) IE of said SETUPmessage.
 9. A non-transitory machine readable medium having instructionswhich when executed by a processing core within an ATM gateway cause amethod to be performed, said method comprising: receiving a call noticefrom a telephony signaling control network to connect through an ATMnetwork including said ATM gateway, the call notice including TDMparameters including information indicative of a TDM time slot overwhich a call will be carried and information indicative of a trunk linethat couples an ATM source gateway to a telephony network, the TDM timeslot being associated with the trunk line that couples the ATM sourcegateway to the telephony network; in response to the receiving the callnotice sending identification of said ATM gateway and ATM-TDMcorrelation tag having information that associates an ATM connectionwith the TDM parameters, the ATM connection being used to transport thecall; and, in response to a message having said ATM-TDM correlation taghaving been received from another node in said ATM network, using saidATM-TDM correlation tag to correlate said call with a switched virtualcircuit within said ATM network that said message was sent to establishso that said call's traffic will be carried by said switched virtualcircuit.
 10. The machine readable medium of claim 9 wherein said messageis an ATM SETUP message.
 11. The machine readable medium of claim 10wherein said correlation tag is within a Called Party Sub AddressInformation Element (IE) of said SETUP message.
 12. The machine readablemedium of claim 10 wherein said correlation tag is within a GenericIdentifier Transport (GIT) IE of said SETUP message.
 13. The machinereadable medium of claim 10 wherein said correlation tag is within aGeneric Application Transport (GAT) IE of said SETUP message.
 14. Themachine readable medium of claim 10 wherein said correlation tag iswithin a User to User IE of said SETUP message.
 15. The machine readablemedium of claim 10 wherein said correlation tag is within a Network CallCorrelation Identifier (NCCI) IE of said SETUP message.
 16. The machinereadable medium of claim 10 wherein said correlation tag is within aCalling Party Sub Address IE of said SETUP message.
 17. The machinereadable medium of claim 10 wherein said correlation tag is within aServed User Generated Reference (SUGR) IE of said SETUP message.
 18. Themachine readable medium of claim 10 wherein said method furthercomprises sending a CONNECT message to said another node to establishsaid switched virtual circuit.
 19. An ATM gateway, comprising: means forreceiving a call notice from a telephony signaling control network toconnect through an ATM network including said ATM gateway, the callnotice including TDM parameters that include information indicative of aTDM time slot over which a call will be carried and informationindicative of a trunk line that couples an ATM source gateway to atelephony network, the TDM time slot being associated with the trunkline that couples the ATM source gateway to the telephony network; meansfor sending identification of said ATM gateway and an ATM-TDMcorrelation tag having information that associates an ATM connectionwith the TDM parameters, the ATM connection being used to transport thecall, the sending responsive to the receiving the call notice from thetelephony signaling control network; and, means for using saidcorrelation tag to correlate said call with a virtual circuit withinsaid ATM network that said message was sent to establish so that saidcall's traffic will be carried by said virtual circuit, the usingresponsive to receiving a message from another node in said ATM network,the message including said ATM-TDM correlation tag.
 20. The ATM gatewayof claim 19 wherein said message is an ATM SETUP message.
 21. The ATMgateway of claim 20 wherein said correlation tag is within a CalledParty Sub Address Information Element (IE) of said SETUP message. 22.The ATM gateway of claim 20 wherein said correlation tag is within aGeneric Identifier Transport (GIT) IE of said SETUP message.
 23. The ATMgateway of claim 20 wherein said correlation tag is within a GenericApplication Transport (GAT) IE of said SETUP message.
 24. The ATMgateway of claim 20 wherein said correlation tag is within a User toUser IE of said SETUP message.
 25. The ATM gateway of claim 20 whereinsaid correlation tag is within a Network Call Correlation Identifier(NCCI) IE of said SETUP message.
 26. The ATM gateway of claim 20 whereinsaid correlation tag is within a Calling Party Sub Address IE of saidSETUP message.
 27. The ATM gateway of claim 20 wherein said correlationtag is within a Served User Generated Reference (SUGR) IE of said SETUPmessage.
 28. An ATM source gateway, comprising: a communicationinterface to: receive notification of a call from a telephony signalingcontrol network, the notification identifying a TDM time slot over whichsaid call will be carried, said TDM time slot on an trunk line thatcouples the ATM source gateway to the telephony network; send ATM sourceidentification and an ATM-TDM correlation tag having information thatassociates an ATM connection that will be used to transport a call withTDM parameters that will be used to transport the call to the telephonysignaling control network; and receive a SETUP message with said ATM-TDMcorrelation tag from an ATM destination gateway; and a mapping table toreflect that a VPI/VCI address received in the SETUP message correspondsto said TDM time slot.
 29. The ATM source gateway of claim 28, whereinthe communication interface further sends a CONNECT message to said ATMdestination gateway after receiving said SETUP message.